Inductors are circuit elements that operate based on magnetic fields. The source of the magnetic field is charge that is in motion, or current. If current varies with time, the magnetic field that is induced also varies with time. A time-varying magnetic field induces a voltage in any conductor that is linked by the magnetic field. If the current is constant, the voltage across an ideal inductor is zero. Therefore, the inductor looks like a short circuit to a constant or DC current. In the inductor, the voltage is given by:
  v  =      L    ⁢                  ⁢                            ⅆ          i                          ⅆ          t                    .      Therefore, there cannot be an instantaneous change of current in the inductor.
Inductors can be used in a wide variety of circuits. Power inductors receive a relatively high DC current, for example up to about 100 Amps, and may operate at relatively high frequencies. For example and referring now to FIG. 1, a power inductor 20 may be used in a DC/DC converter 24, which typically employs inversion and/or rectification to transform DC at one voltage to DC at another voltage.
Referring now to FIG. 2, the power inductor 20 typically includes one or more turns of a conductor 30 that pass through a magnetic core material 34. For example, the magnetic core material 34 may have a square outer cross-section 36 and a square central cavity 38 that extends the length of the magnetic core material 34. The conductor 30 passes through the central cavity 38. The relatively high levels of DC current that flow through the conductor 30 tend to cause the magnetic core material 34 to saturate, which reduces the performance of the power inductor 20 and the device incorporating it.